Fingerprint sensing and matching is a reliable and widely used technique for personal identification or verification. In particular, a common approach to fingerprint identification involves scanning a sample fingerprint or an image thereof and storing the image and/or unique characteristics of the fingerprint image. The characteristics of a sample fingerprint may be compared to information for reference fingerprints already in a database to determine proper identification of a person, such as for verification purposes.
A particularly advantageous approach to fingerprint sensing is disclosed in U.S. Pat. No. 5,953,441 to Setlak and assigned to the assignee of the present invention, the entire contents of which are herein incorporated by reference. The fingerprint sensor is an integrated circuit sensor that drives the user's finger with an electric field signal and senses the electric field with an array of electric field sensing pixels on the integrated circuit substrate.
U.S. Pat. No. 6,289,114 to Mainguet, which is assigned to the assignee of the present invention and is incorporated in its entirety by reference discloses a fingerprint sensor that includes a finger sensing integrated circuit (IC). The finger sensing IC includes a layer of piezoelectric or pyroelectric material placed between upper and lower electrodes to provide electric signals representative of an image of the ridges and valleys of the fingerprint.
A particularly advantageous approach to multi-biometric fingerprint sensing is disclosed in U.S. Pat. No. 7,361,919 to Setlak, which is assigned to the assignee of the present invention and is incorporated in its entirety by reference. The Setlak patent discloses a multi-biometric finger sensor sensing different biometric characteristics of a user's finger that have different matching selectivities.
A fingerprint sensor may be particularly advantageous for verification and/or authentication in an electronic device, and more particularly, a portable device, for example. Such a fingerprint sensor may be carried by the housing of a portable electronic device, for example, and may be sized to sense a fingerprint from a single-finger. For example, the AES3400 sensor from AuthenTec, Inc. of Melbourne, Fla., is widely used in a variety of notebooks, desktops and PC peripherals. Other fingerprint sensors, for example, the AES850, also from AuthenTec, Inc. of Melbourne, Fla., is a multi-function smart sensor that expands touch-based functionality of touchscreen and QWERTY smartphones with a reduced impact on sensor performance or durability.
When using a semiconductor fingerprint sensor, or integrated circuit fingerprint sensor, in a portable electronic device, for example, a mobile telephone, it may be desirable to locate the integrated circuit of the fingerprint sensor separately from the finger sensing region. Separating the finger sensing integrated circuit (IC) from the finger sensing area may be particularly advantageous when the finger sensing area is relatively thin and transparent so that it may be placed over the top of a display of the portable electronic device, and wherein the IC may be located in a nearby non-display region of the portable electronic device.
A relatively high quality electronic fingerprint sensor includes the finger sensing region directly above the IC of the fingerprint sensor. In the current art, a lower quality fingerprint sensor may operate with the finger sensing area region separated from the IC, but the fingerprint sensor often may experience problems operating in the display region. The lower quality fingerprint sensor is typically unable to capture fingerprint images through a relatively thick protective cover used over the display regions of portable electronic devices. Thus, the images that are captured are more noisy and lower quality, which may lead to unacceptable biometric performance.
U.S. Pat. No. 8,005,276 to Dean et al. discloses a fingerprint sensing circuit for reducing noise and parasitic capacitive coupling. A fingerprint sensing area including transmitting and receiving elements may be physically decoupled from the fingerprint sensing circuit. Positioning the sensing elements off the silicon die may improve the reliability of the fingerprint sensor by reducing the sensor's susceptibility to electrostatic discharge, wear, and breakage.
U.S. Patent Application Publication No. 2011/0102569 to Erhart discloses a fingerprint sensor that includes multiple fingerprint sensor lines on a surface of an LCD. The LCD is covered on an opposite surface with motion sensing lines.